Thermoplastic mixture comprising an agent to improve the lacquer bonding

ABSTRACT

A polymer mixture on the basis of a polyalkylene phthalate ester, a copolyether ester and an agent to improve the impact to which an agent to improve the bonding of lacquer systems on an aqueous base has been added. The polymer mixture according to the invention comprises a polyalkylene glycol polymer or a polyalkylene glycol copolymer as an agent to improve the lacquer bonding.

This is a divisional of application Ser. No. 07/975,151 filed on Nov.12, 1992 U.S. Pat. No. 5,382,454 which is a continuation of Ser. No.07/682,769 filed Apr. 9, 1990 now abandoned.

The invention relates to a polymer mixture comprising A) a polyalkylenephtalate ester, B) a copolyether ester, C) an agent to improve theimpact strength and D) an agent to improve the bonding of aqueouslacquer systems upon the surface of articles moulded out of the polymermixture.

Polymer mixtures are now being used on a large scale to manufacturetherefrom parts by means of various treatments, for example, injectionmoulding and extrusion.

It is sometimes desired to provide the formed parts with a decorativeand/or protective layer of lacquer. In this connection the bonding ofthe lacquer layer to the formed articles constitutes a problem.

Of late, an increasing number of lacquer systems on a aqueous basis areused. The solutions which have been found to improve the bonding oflacquer systems on the basis of organic solvents often are notsatisfactory to improve the bonding of aqueous lacquer systems.

One of the possibilities to improve the bonding of lacquer systemsconsists in that compounds are processed in the polymer mixture whichcontribute to an improvement of the lacquer bonding.

The invention is based on the discovery that certain groups of compoundsare suitable to improve the bonding of aqueous lacquer systems toarticles formed from polyalkylene phthalate ester blended with otherpolymers. These compounds are preferably incorporated in the polymermixture.

The invention therefore relates to certain polymer mixtures and articlesmolded therefrom, by injection molding or extrusion.

The particular aspect of the polymer mixture according to the inventionis that it comprises a polyalkylene glycol polymer or polyalkyleneglycol copolymer as an agent to improve the lacquer bonding.

The polymer mixture according to the invention preferably comprises:

35-70% by weight of component A;

15-50% by weight of component B;

5-25% by weight of component C and 0.1-10% by weight of component D.

with respect to the total quantity of components A,B, C and D.

U.S. Pat. No. 3,948,831 and Chemical Abstracts, vol. 73, no. 18 of Nov.2, 1970, page 63, abstract 89085j, describe the treatment of polyesterwith polyalkylene glycols to improve the dyeability of fibers formedfrom such polyesters. Applying an aqueous lacquer onto the surface of anarticle molded out of the polymer is a quite difference process fromdying fibres made out of a polyester.

EP-A-0386 256 corresponding with WO 90/01520 describes fibres made outof polyester or out of copolyether esters which have been treated with avery special type of polyoxyethylene polyethers to render them moistureabsorbent and give them a good color fastness.

U.S. Pat. No. 4,540,749 describes the addition of polyethylene glycolsto low melting blends of polyesters to decrease the minimum bondingtemperature and to decrease the melt viscosity.

NL-A-68 13042, corresponding with GB-A-1,217,423, describes the additionof aliphatic polyethers to polyesters, to improve the impact strengththereof. The added polyethers have a high molecular weight of 5,000 to1,000,000, preferably of 10,000 to 100,000.

EP-A-0,248,352 describes compositions of a polyester, an elastomer and ablock copolyester. Nothing is said about adding additives enhance thebonding strength to lacquer systems.

U.S. Pat. No. 4,622,263 describes block-copolyether esters which may beblended with a polyalkylene glycol. The described block-copolyetheresters as well as described blends have a high water absorbance.

The polymer mixture according to the invention comprises at any rate oneor more of the following constituents:

A. a polyalkylene phthalate ester and

B. a copolyether ester

C. an agent to improve the impact strength

D. a polyalkylene glycol polymer or copolymer.

A. Polyalkylene phthalate

Polyalkylene phthalate esters are esters derived from one or morealkanediol compounds and one or more aromatic dicarboxylic acids.

A part of the aromatic dicarboxylic acids may be replaced by analiphatic dicarboxylic acid. It is also possible to replace a part ofthe diol compounds by a polyol compound and/or a part of thedicarboxylic acid compound by a polycarboxylic acid.

The best suitable polyalkylene phthalate esters are the esters the diolcomponent of which is derived for 80 mol % or more from butane-1,4-dioland the dicarboxylic acid component of which is derived for 80 mol % ormore from terephthalic acid. The polyalkylene phtalate ester preferablyhas a melting point above 200° C.

B. Copolyether ester

Copolyether ester polymers are to be understood to mean herein blockcopolymers having a hard ester block and a soft elastomeric ether block.Examples of such block copolymers are described, for example, in U.S.Pat. No. 4,778,855.

C. Agent to improve the impact strength

As agents to improve the impact strength are to be considered inprinciple any agents which are suitable to improve the impact strengthof polyalkylene phthalate esters. By way of example may be mentioned thegraft copolymers which can be obtained by grafting one or more monomers,for example, styrene, acrylonitrile, an acrylic or methacrylic ester,methacrylic acid, maleic acid on a rubber-like latex, for example, abutadiene latex, a styrene butadiene latex, an acrylate latex.

D. Polyalkylene glycol polymer or polyalkylene glycol copolymer.

Polyalkylene glycol polymer or copolymers are compounds known per se.Their preparation and various applications of these polymers aredescribed, for example, in Kirk-Othmer, Encyclopedia of ChemicalTechnology, 3rd edition, volume 18, pp. 616-645.

These polymers may be obtained by polymerisation of one or moredifferent alkene oxides, for example, ethylene oxide and/or propyleneoxide and/or butylene oxide. The molecular weight may be chosen between200 and 10,000. Block copolymers with propylene oxide blocks andethylene oxide blocks are preferably used. The alkylene units incomponent D preferably comprise not more than four carbon atoms. Thepolymer mixture according to the invention may moreover compriseconventionally used additives, for example, stabilisers, agents toimprove the flame-retardant properties, fillers, release agents,pigments and dyes, reinforcing fibres, and the like.

The polymer mixture according to the invention can be obtained accordingto any conventionally used method of preparing polymer mixtures. Theindividual components are preferably mixed together in the melt in anextruder (compounded). The extrudate (in strand form) which emanatesfrom the extruder is then chopped up to pellets. The pellets may befurther processed, for example, in an injection moulding machine.

Examples I to V; comparative example A

Various polymer mixtures were prepared starting from the followingconstituents:

PBT: a polybutylene terephthalate ester having an intrinsic viscosity of0.775 dl/gram measured in a 60/40 mixture of phenol and tetrachloroethane at 25° C.

copoly--a polyether ester of the type as described in ether U.S. Pat.No. 4,778,855, derived from dimethyl ester: terephthalate, poly(tetramethylene oxide) diol and a mixture of butane diol and hexanediol.

ABS: A graft copolymer comprising approximately 70% by weight ofpolybutadiene rubber on which styrene and acrylonitrile have beengrafted.

peg: polyethylene glycol having a molecular weight of approximately3350.

pepg-1: a poly [propylene oxid-ethylene oxid] block copolymer havingapproximately 30% of polyethylene oxide; molecular weight polypropyleneoxide block: approximately 1100; molecular weight of block copolymerapproximately 1700.

pepg-2: a poly [propylene oxid-ethylene oxid] block copolymer havingapproximately 50% of polyethylene oxide; molecular weight polypropyleneoxide block: approximately 3250; molecular weight of block copolymerapproximately 6500.

ST: a mixture of conventionally used stabilisers.

The various constituents were compounded in a Werner and Pfleidererextruder in the quantities as indicated in the table hereinafter. Theresulting extrudate was chopped up. Test plates to determine the lacquerbonding (dimension: 175×175 mm, thickness 3 mm) were injection mouldedfrom the pellets.

The surface of the plates was painted by means of a spray gun. Thelacquer used was a commercially available aqueous primer (succeeded bydrying at 80° C. for 15 minutes). A top layer was provided on theprimer. The painted plates were cured at 80° C. for 45 minutes and thenconditioned at 50° C. for 48 hours. The bonding strength was thendetermined according to ISO 6270 (after storing in a moist atmospherefor 96 hours). In the test, TESA TAPE 4651 was manually pressed on thepainted surface. The TESA TAPE was then pulled off the surface. Thesurface was evaluated visually. Evaluation "Gto" indicates a goodbonding; evaluation "Gt5" indicates a poor bonding.

A further test to determine the lacquer bonding was carried out asfollows: a polycarbonate strip having a width of 17 mm (effectivebonding width 15 mm) was adhered to the painted plates by means of acyanoacrylate glue. The force required to pull off the polycarbonatestrip in a direction vertical to the lacquered surface (with the lacquerlayer adhered thereto) was measured in a tensile testing machine. Theresult is indicated as bonding strength (N/15 mm).

The results obtained are also recorded in the table hereinafter.

It may be seen from the results obtained that the lacquer bonding isconsiderably improved by the addition of polyalkylene glycol.

                                      TABLE                                       __________________________________________________________________________    Example    A    I    II   III  B    IV                                        __________________________________________________________________________    Composition                                                                   (parts by weight)                                                             ∘                                                                   PBT      99.2 97.2 98.2 98.2 49.2 47.2                                      ∘                                                                   Copolyether                                                                            --   --   --   --   35   35                                          ester                                                                       ∘                                                                   ABS      --   --   --   --   15   15                                        ∘                                                                   peg      --   2    --   --   --   2                                         ∘                                                                   pepg-1   --   --   1    --   --   --                                        ∘                                                                   pepg-2   --   --   --   1    --   --                                        ∘                                                                   ST       0.8  0.8  0.8  0.8  0.8  0.8                                       Results:                                                                      . lacquer  2 × GTo                                                                      5 × GT5                                                                      5 × GTo                                                                      5 × GTo                                                                      5 × GTo                                                                      5 × GTo                               bonding  +                                                                    acc.to   3 × GT5                                                        ISO 2409                                                                    . lacquer  1 × GT2                                                                      2 × GTo                                                                      2 × GTo                                                                      2 × GTo                                                                      2 × GTo                                                                      3 × GTo                               acc.to   +                                                                    ISO 6270 1 × GT5                                                      . bonding  <not determined →                                                                          17   39                                          strength                                                                      Newton per                                                                    15 mm                                                                       __________________________________________________________________________

We claim:
 1. A polymer mixture comprising A) a polyalkylene phthalateester, B) a copolyether ester block copolymer, C) a polymeric agent toimprove impact strength and D) an agent to improve the bonding ofaqueous lacquer systems upon the surface of articles moulded out of thepolymer mixture, wherein, the polymer mixture comprises as an agent toimprove said bonding a polyalkylene glycol polymer or a polyalkyleneglycol copolymer.
 2. A polymer mixture according to claim 1, wherein,the polymer mixture comprises:35-70% by weight of component A; 15-50% byweight of component B; 5-25% by weight of component C and 0.1-10% byweight of component D.with respect to the total quantity of componentsA,B, C and D.
 3. A polymer mixture according to claim 1, wherein, thealkylene units of component D comprise not more than four carbon atoms.4. A polymer mixture according to claim 1, wherein, component C is agraft copolymer obtained by grafting one or more monomers on arubber-like latex.
 5. Articles molded out of the polymer mixtureaccording to claim 1.